ASTM D4784-93(1998)

Standard for LNG Density Calculation Models

SCOPE
1.1 This standard covers LNG density calculation models  for use in the calculation or prediction of the densities of saturated LNG mixtures from 90 to 120K to within 0.1% of true values given the pressure, temperature, and composition of the mixture.
1.2 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-May-1998
• Technical Committee: D03 - Gaseous Fuels
• Drafting Committee: D03.08 - Thermophysical Properties

Relations

• Replaced By: ASTM D4784-93(2003) - Standard for LNG Density Calculation Models
• Effective Date: 10-May-2003
• Referred By: ASTM D7551-10(2015) - Standard Test Method for Determination of Total Volatile Sulfur in Gaseous Hydrocarbons and Liquefied Petroleum Gases and Natural Gas by Ultraviolet Fluorescence
• Effective Date: 10-May-1998

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 4784 – 93 (Reapproved 1998)
Standard for
LNG Density Calculation Models
This standard is issued under the fixed designation D 4784; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This standard is a description of four mathematical models of the equation of state for LNG-like
mixtures that were adopted in 1988. The four models include an extended corresponding states model,
a cell model, a hard sphere model, and a revised Klosek and McKinley model. Each of the models has
been optimized to the same experimental data set which included data for pure nitrogen, methane,
ethane, propane, iso and normal butane, iso and normal pentane, and mixtures thereof. For LNG-like
mixtures (mixtures of the orthobaric liquid state at temperatures of 120K or less and containing at least
60 % methane, less than 4 % nitrogen, less than 4 % each of iso and normal butane, and less than 2 %
total of iso and normal pentane), all of the models are estimated to predict densities to within 0.1 %
of the true value. These models were developed by the National Institute of Standards and Technology
(formerly the Bureau of Standards) upon culmination of seven years of effort in acquiring physical
properties data, performing extensive experimental measurements using specially developed equip-
ment, and in using these data to develop predictive models for use in density calculations.
1. Scope
methane 60 % or greater
nitrogen less than 4 %
1.1 This standard covers LNG density calculation models
n-butane less than 4 %
for use in the calculation or prediction of the densities of
i-butane less than 4 %
pentanes less than 2 %
saturated LNG mixtures from 90 to 120K to within 0.1 % of
true values given the pressure, temperature, and composition of
It is assumed that hydrocarbons with carbon numbers of six
the mixture.
or greater are not present in the LNG solution.
1.2 This standard does not purport to address all of the
3. Models
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.1 Extended Corresponding States—The extended corre-
priate safety and health practices and determine the applica-
sponding states method is defined by the following equations:
bility of regulatory limitations prior to use.
Z @P,T# 5 Z @Ph /f , T/f # (1)
i o ii,o ii,o ii,o
2. Significance and Use G @P,T# 5 f G @Ph /f , T/f # 2 RT ln ~h ! (2)
i ii,o o ii,o ii,o ii,o ii,o
2.1 The models in this standard can be used to calculate the
where:
density of saturated liquid natural gas in the temperature range
Z = compressibility factor,
90 to 120K. The estimated uncertainty for the density calcula-
G = Gibbs free energy,
tions is 60.1 %. The restrictions on composition of the
P = pressure,
liquefied natural gas are:
T = temperature,
o = reference fluid, and
i = fluid for which properties are to be obtained via the
This standard is under the jurisdiction of ASTM Committee D-3 on Gaseous
equation of state for the reference fluid and the
Fuels and is the direct responsibility of Subcommittee D03.08 on Thermophysical
Properties.
transformation functions f and h are introduced to
ii,o ii,o
Current edition approved March 15, 1993. Published May 1993. Originally
allow extension of the method to mixtures.
published as D 4784 – 88. Last previous edition D 4784 – 88.
The two defining Eq 1 and Eq 2 are necessary since there are
The formulation of the models and the supporting work was done by the
National Bureau of Standards under the sponsorship of British Gas Corp., Chicago two transformation functions. In this case, an equation of state
Bridge and Iron Co., Columbia Gas Service Corp., Distrigas Corp., Easco Gas LNG,
for methane was chosen for the reference fluid. During the
Inc., El Paso Natural Gas, Gaz de France, Marathon Oil Co., Mobil Oil Corp.,
course of the study it was necessary to modify the equation of
Natural Gas Pipeline Co., Phillips Petroleum Co., Shell International Gas, Ltd.,
state to give a realistic vapor liquid phase boundary down to a
Sonatrach, Southern California Gas Co., Tennessee Gas Pipeline, Texas Eastern
Transmission Co., Tokyo Gas Co., Ltd., and Transcontinental Gas Pipe Line Corp.,
temperature of 43K. This modification was necessary to
through a grant administered by the American Gas Association, Inc.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4784
accommodate the very low reduced temperatures of the heavier b 5 b x x (13)
m ( ( ij i j
i j
hydrocarbons and was accomplished without changing the
performance of the equation of state above the triple point of
c 5 c x x (14)
( (
m ij i j
methane. The f and h are defined as
i j
ii,o ii,o
c c
f 5 ~T /T ! u ~T ,V ! (3) The mixing rules are:
ii,o ii o ii,o r r
i i
1/3 1/3 3
and b 1 b
ii jj
b 5 1 2 j ! (15)
F ~ G
ij ij
c c
h 5 V /V f T ,V (4)
~ ! ~ !
ii,o ii,o o ii,o r r
i i
2 1/2
b
1/2 ij
where: a 5 ~a a ! ~1 2 k ! (16
...